ISC SSCP Online Access

To assist in Intrusion Detection you would review audit logs for access violations.

The following answers are incorrect:

access control lists. This is incorrect because access control lists determine who has access to what but do not detect intrusions.

security clearances. This is incorrect because security clearances determine who has access to what but do not detect intrusions.

host-based authentication. This is incorrect because host-based authentication determine who have been authenticated to the system but do not dectect intrusions.

This type of IDS is called a network-based IDS because monitors network traffic in real time.

Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 48.

Accountability can actually be seen in two different ways:

1) Although audit trails are also needed for accountability, no user can be accountable for their actions unless properly authenticated.

2) Accountability is another facet of access control. Individuals on a system are responsible for their actions. This accountability property enables system activities to be traced to the proper individuals. Accountability is supported by audit trails that record events on the system and network. Audit trails can be used for intrusion detection and for the reconstruction of past events. Monitoring individual activities, such as keystroke monitoring, should be accomplished in accordance with the company policy and appropriate laws. Banners at the log-on time should notify the user of any monitoring that is being conducted.

The point is that unless you employ an appropriate auditing mechanism, you don't have accountability. Authorization only gives a user certain permissions on the network. Accountability is far more complex because it also includes intrusion detection, unauthorized actions by both unauthorized users and authorized users, and system faults. The audit trail provides the proof that unauthorized modifications by both authorized and unauthorized users took place. No proof, No accountability.

Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Page 50.

The Shon Harris AIO book, 4th Edition, on Page 243 also states:

Auditing Capabilities ensures users are accountable for their actions, verify that the secutiy policies are enforced,

and can be used as investigation tools. Accountability is tracked by recording user, system, and application activities.

This recording is done through auditing functions and mechanisms within an operating sytem or application.

Audit trail contain information about operating System activities, application events, and user actions.

Traffic anomaly-based is the correct choice. An anomaly based IDS can detect unknown attacks. A traffic anomaly based IDS identifies any unacceptable deviation from expected behavior based on network traffic.

Protocol anomaly based is not the best choice as while a protocol anomaly based IDS can identify unknown attacks, this type of system is more suited to identifying deviations from established protocol standards such as HTTP. This type of IDS faces problems in analyzing complex or custom protocols.

Pattern matching is not the best choice as a pattern matching IDS cannot identify unknown attacks. This type of system can only compare packets against signatures of known attacks.

Stateful matching is not the best choice as a statful matching IDS cannot identify unknown attacks. This type of system works by scanning traffic streams for patterns or signatures of attacks.